Jack



FIG. 1 is a perspective view of a jack showing my new design, showing the jack mounted to a tractor in a lowered, operative position;

FIG. 2 is a rear elevational view thereof;

FIG. 3 is a front elevational view thereof;

FIG. 4 is a side elevational view thereof, the opposite side elevational view being a mirror image of that shown;

FIG. 5 is a top plan view thereof; and

FIG. 6 is a bottom plan view thereof.

FIG. 7 is a perspective view thereof, showing the jack mounted to a tractor in a raised, stowed position;

The broken lines shown in FIGS. 1 and 7 are for illustration purposes only and form no part of the claimed design. 

The ornamental design for a jack, as shown and described. 